1. Field of the Invention
The present invention relates to an organic light-emitting display device and a method of manufacturing the same, and more particularly, to an organic light-emitting display device including a pad portion which is connected to a drive integrated circuit (IC) chip and a method of manufacturing the organic light-emitting display device.
2. Description of the Related Art
The rapid development of the information and technology (IT) industry is dramatically increasing the use of display devices. Recently, there have been demands for display devices that are lightweight and thin, consume low power and provide high resolution. To meet these demands, liquid crystal displays or organic light-emitting displays using organic light-emitting characteristics are being developed.
Organic light-emitting displays, which are next-generation display devices having self light-emitting characteristic, have better characteristics than liquid crystal displays in terms of viewing angle, contrast, response speed and power consumption, and can be manufactured to be thin and lightweight since a backlight is not required.
An organic light-emitting display includes a substrate having a pixel region and a non-pixel region and a container or another substrate which is placed to face the substrate for encapsulation and attached to the substrate by a sealant such as epoxy. In the pixel region of the substrate, a plurality of organic light-emitting diodes (OLEDs) are connected in a matrix pattern between scan lines and data lines to form pixels. In the non-pixel region, the scan lines and the data lines extending from the scan lines and the data lines of the pixel region, power source supply lines (not shown) for operating the organic light-emitting diodes, and a scan driver and a data driver for processing signals received from an external source via input pads and providing the processed signals to the scan lines and the data lines are formed. The scan driver and the data driver respectively include driving circuits for processing signals transmitted from the external source and generating scan signals and data signals. The scan driver and the data driver may be formed in the process of manufacturing the OLEDs or may be manufactured as additional integrated circuit (IC) chips to be mounted on a substrate.
When the scan driver and the data driver are manufactured as additional IC chips to be mounted on a substrate, the drive IC chips may be mounted using a tape automated bonding method in which the drive IC chips are mounted on a tape carrier package (TCP) and connected to pads of the substrate or using a chip on glass (COG) method in which the driver IC chips are attached directly to the pads of the substrate. The COG method ensures a simpler structure and requires a smaller area than the TAB method. Thus, the COG method is widely employed for small and medium sized display panels of mobile telecommunications products.
In the COG method, bumps formed on input and output terminals of a drive IC chip are connected to an inner lead bonding (ILB) pad and an outer lead bonding (OLB) pad formed on a substrate by conductive balls contained in an anisotropic conductive film (ACF).
An input pad coupled to the ILB pad is connected to a flexible printed circuit (FPC). In response to control and data signals supplied from an external source through the FPC, the drive IC chips generate scan and data signals and provide the generated scan and data signals to the OLEDs via the scan lines and the data lines connected to the OLB pad.
A pad portion included in a conventional organic light-emitting display device has a flat surface. Therefore, the pad portion is electrically connected to a drive IC chip thereabove by a plurality of conductive balls and receives signals from an external source through the driver IC chip.
When a thickness of a conductive layer exposed through the surface of the pad portion is greater than 300 Å, it is not easy to etch the metal or indium tin oxide (ITO) that forms the conductive layer, and a stronger acid is required to etch a thicker conductive layer. Therefore, a thicker conductive layer leads to the risk of using a stronger acid that cannot be handled easily and is harmful to workers.
For this reason, the conductive layer may be formed to a thickness of less than 300 Å. However, as the conductive layer becomes thinner, the difference between the contact resistance and surface resistance of the conductive layer increases due to film dispersion, and the increased difference degrades the reliability of the organic light-emitting display device when in operation.